A recent article investigates the association between vitamin D status and the incidence of sepsis and subsequent mortality, using a large, population-based prospective cohort derived from the U.K. Biobank.
Sepsis, a life-threatening organ dysfunction caused by a dysregulated immune response to infection, represents a major global health burden with high mortality, significant healthcare costs, and prolonged hospital stays. Given the immunomodulatory properties of vitamin D and the overlap in risk factors between vitamin D deficiency and sepsis, the study aimed to clarify whether serum vitamin D levels influence sepsis risk and outcomes.
The study included 444,509 participants aged 40–69 years. Serum 25-hydroxyvitamin D [25(OH)D] concentrations were measured at baseline and categorised into three groups: severe deficiency (<10 ng/mL), deficiency (10–20 ng/mL), and sufficiency (>20 ng/mL). Participants were followed for a mean of 14 years. Mortality outcomes were assessed at 28 days, 60 days, and one year following sepsis diagnosis.
The results demonstrate a clear inverse relationship between vitamin D levels and sepsis risk. Over the follow-up period, 15,452 cases of sepsis were recorded. Individuals with severe vitamin D deficiency exhibited a significantly higher risk of developing sepsis compared with those with sufficient levels. Even moderate deficiency was associated with increased risk, though to a lesser degree. Each incremental increase in vitamin D concentration was associated with a modest reduction in sepsis risk, suggesting a dose–response relationship.
Subgroup analyses revealed that the association was consistent across most demographic and clinical groups, but was significantly modified by sex and body mass index (BMI). The protective effect of higher vitamin D levels was stronger in females than in males, and in individuals with normal BMI (<25 kg/m²) compared with those who were overweight or obese. These findings suggest that biological factors, such as hormonal influences and differences in vitamin D metabolism or storage, may influence the relationship between vitamin D and immune function.
The study also examined the relationship between vitamin D status and mortality among individuals who developed sepsis. Severe vitamin D deficiency was associated with significantly higher mortality at all measured time points. Specifically, individuals with 25(OH)D levels below 10 ng/mL had increased risks of 28-day, 60-day, and one-year mortality compared with those with sufficient levels. In contrast, moderate deficiency (10–20 ng/mL) was not significantly associated with increased mortality, reinforcing the importance of severe deficiency as a critical threshold.
The authors propose several biological mechanisms to explain these findings. Vitamin D plays a key role in immune regulation, enhancing innate immunity through the production of antimicrobial peptides such as cathelicidin, while also modulating adaptive immune responses. It reduces excessive inflammation by suppressing pro-inflammatory cytokines and promoting regulatory T cell activity. Additionally, vitamin D supports endothelial integrity, which is crucial in preventing the vascular dysfunction characteristic of sepsis. These combined effects provide a plausible explanation for the observed association between low vitamin D levels and increased susceptibility to infection and poor outcomes.
Overall, the study provides strong evidence of a negative and nonlinear association between serum vitamin D levels and the incidence of sepsis and sepsis-related mortality. Severe vitamin D deficiency emerges as a significant independent risk factor, particularly for adverse outcomes. These findings highlight the potential importance of vitamin D status in sepsis prevention and prognosis, while underscoring the need for targeted clinical trials to determine whether correcting deficiency can improve outcomes.
Source: Critical Care
Image Credit: iStock
